1955 Granco FM-610U Tube Radio (pics)

[DavGoodlin]

Originally Posted by Electronic M

One trick I've heard of is to wet the cone then let the speaker dry open end up. After it has dried it should not rub again.

Yes, that worked quite well for me on a 5" round Zenith speaker. I hope you don't need to replace the voice coil

[Robb]

The speaker is blown (distortion)
Here's a picture of the speaker for size reference.
Gonna either fix or replace it.

[Electronic M]

I'd change that 2uF 50V lytic.

[Robb]

Originally Posted by Electronic M

I'd change that 2uF 50V lytic.

The radio was sent out and gone over by a vintage radio service shop.
That is not the issue. The issue is the blown speaker.

BTW, At $31.00+ no way Im paying that for a cap !

http://www.ebay.com/itm/CAP-2UF-50V-...item1c3e417af0

[Jeffhs]

Originally Posted by bob91343

Note that there is no variable tuning capacitor. It moves slugs through coils to tune. A spinoff of the Dumont Inductuner or the Collins PTO.

This concept was probably derived from the Dumont Inputuner. I have three Zenith radios (K731, C845 and Royal 3000-1) that use permeability-tuned coils for FM tuning, no tuning capacitor for that band. There is a tuning cap in each radio, but it is used strictly for AM (and shortwave in the 3000-1). The sensitivity of all three sets is excellent, probably due in large part to the permeability-tuned FM front end.

BTW, I did not realize that Collins also used such tuners in their amateur gear, and I've been in ham radio over 40 years (just renewed my license for another 10-year term). Never could afford Collins gear, but I remember seeing it advertised in QST, and back when the ARRL Handbook had an advertising section way in the back of the book.

[jr_tech]

Originally Posted by bob91343

Note that there is no variable tuning capacitor. It moves slugs through coils to tune. A spinoff of the Dumont Inductuner or the Collins PTO.

No, the "slug tuned" components shown in the excellent close-up photo by Robb are actually sleeve variable capacitors... they are indicated as capacitors on the schematic as well. On the photo you can see the two "plates" of each variable cap and the small trimmer cap soldered between them. The "slugs" increase or decrease the capacitance between the two "plates" to tune the radio. The coils in each L-C are located to the sides of each variable capacitor and are fixed in value.



jr

[Robb]

Anyone know how to remove this speaker ?

[jr_tech]

I'm guessing that the two screws under the chassis by the rectifier hold the speaker. I never took mine out.

jr

[bob91343]

That is a standard 4x6 inch speaker, although I doubt they are made any more. Still, they should be available either NOS or cannibalize.

[Chip Chester]

Before you take the speaker out, try the "spritzing with water" thing -- but allow it to dry with the radio upside down. Nutty, but it's free to try.

Over on AK, there are guys that have a certain hi-fi speaker whose cones "droop" over time. The go-to fix is to rotate the speaker in the cabinet, or just turn them upside down half the time.

Chip

[dieseljeep]

Originally Posted by bob91343

That is a standard 4x6 inch speaker, although I doubt they are made any more. Still, they should be available either NOS or cannibalize.

It's really not a common 4X6" speaker! As you can see, the bottom part of the frame is trimmed off, as part of the frame stamping process. Also, the magnet housing is drilled and tapped, probably for a 8/32 machine screw.
Try the water trick! If it doesn't work, then send it out.

[DaveWM]

or stick a piece of cotton wadding behind the cone, move around to find sweet spot.

[dieseljeep]

Originally Posted by Robb

The radio was sent out and gone over by a vintage radio service shop.
That is not the issue. The issue is the blown speaker.

BTW, At $31.00+ no way Im paying that for a cap !

http://www.ebay.com/itm/CAP-2UF-50V-...item1c3e417af0

Looking at the under chassis views, they either didn't do anything to it or they did the finest job of duplicating the original soldering job. I vote for the former.
BTW, the resistor above the left IF transformer, looks a little cooked. Also the speaker isn't blown. If it was, you wouldn't get any sound at all. All you have is a voice coil rub, due to a warped cone.

[Reece]

I have fixed plenty of speakers with the water trick. Get some water in a cup. Using your finger or a small brush, dampen the whole cone. Keep water out of the voice coil area. Set the radio with the cone facing UP towards the ceiling and let dry overnight. Be sure it's completely dry and try it the next day. You have nothing to lose.

[maxhifi]

Dude that cap is not worth more than $0.50, you have lots of resources in Toronto too, forget eBay. I suggest going here http://www.a1parts.com/ they have all kinds of cool stuff not on the website. I bought a bunch of loose capacitors there really cheaply. It's worth a trip to the store just to check out the massive stock of old and weird electronics as well as the new components.

Here's the cap you need http://www.a1parts.com/capxon/index.html 2.2uF 50V. $0.24 each.The radio will sound like crap if that cap is dried up, but yes it could also be the speaker.

Why not disconnect one lead to the speaker and try to hook it up to something else (like a stereo at low volume), just to double check that the speaker really is bad, before getting it all wet.